The present invention relates to a liquid applicator which contains a small quantity of a liquid used for medical, cosmetic, office, cooking, mechanical processing, or cleaning purpose and which has an applicator member, the applicator being capable of properly and effectively applying such a liquid to an objective part of a living body, office paper, coking instrument, machine or a cleaning object.
Hitherto, medical liquid applicators have been known which include containers for containing the liquid and applicator members associated with the containers. There are two types of such medical liquid applicators: a type in which a brush is provided on the cap of the container and a type having an applicator member held on the container. The applicator incorporating a brush is difficult to handle and is disadvantageous in that the bristles of the brush tend to stimulate an affected part of the living body. On the other hand, the second-mentioned type requires that the container can be deformed to enable the liquid to be squeezed out of the applicator member, through this type of liquid applicator can be handled more easily. Therefore, most of the known medical liquid applicators comprise a container made of a deformable material, e.g., a plastic, and an applicator member fixed on the container.
In the medical liquid applicator of the type mentioned above, since the container material is limited to a deformable material such as a plastic which enables squeezing out the liquid, it is not possible to use a glass as the container material, despite that the glass exhibits various advantages such as resistance to a serialization process, prevention of scattering of volatile solvent or volatile agent, prevention of absorption of medicine, and so forth.
Furthermore, in order that the container having a small volume can exhibit the deformability particular to the materials, it is necessary that the container wall has a smaller wall thickness as compared with containers of large volume or that the container material is soft and flexible. The ratio between the surface area of the container and the volume of the container varies in inverse proportion to the 1/3 order of the volume, so that the ratio of the surface area to the volume increases as the volume is decreased. This means that containers of smaller volume exhibit a greater rate of evaporation/scattering of the liquid per unit volume. For instance, in order for a small container having a volume of 1 ml to exhibit the same rate of evaporation/scattering as that of a container having a volume of 10 ml, it is necessary that the smaller container have a wall thickness which is 2.15 times as large as that of the greater container or, alternatively, that the smaller container is made of a material having lower permeability and, hence, a higher rigidity. Thus, production of a container having a small volume and large deformability is encountered with a problem in that two incompatible requirements must be met simultaneously: namely, the use of a thinner or more flexible material than that of the large container to provide large deformability and the use of thickener and more rigid material to prevent evaporation/scattering. It is therefore difficult to reduce the volume of the container of the conventional medical liquid applicator having an applicator member fixed on the container, in order to prevent evaporation/scattering of the liquid.
JP.U.57-184781 discloses an applicator in which an end valve with an applicator member fixed to one end thereof is held in pressure contact with the opening of a liquid chamber such that the applicator member projects from the body of the applicator. In this known applicator, when the liquid is applied by the applicator member, the end valve is pressed to keep the opening of the applicator chamber open to allow the liquid to be discharged continuously, so that an excess amount of liquid is dispensed. This known liquid applicator, therefore, cannot apply the liquid in such a manner that only a predetermined quantity of liquid exudes and be spread into a very thin film of the liquid.
An object of the present invention is to provide a liquid applicator which has a container of any desired volume and made of a rigid and hard material and which allows only a predetermined quaintly of the liquid to exude to the outer surface of the container and be spread properly and effectively over an objective part.